1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to an in-plane switching mode liquid crystal display device (LCD). Although the present invention is suitable for a wide scope of applications, it is particularly suitable for improving the quality of picture image.
2. Discussion of the Related Art
As a thin film transistor liquid crystal display device (TFT-LCD) has been widely used for portable televisions or notebook computers, an LCD having a large panel is in great demand. A conventional TFT-LCD, however, has a problem that a contrast ratio is changed with a direction of viewing-angle. Liquid crystal display devices such as a twisted nematic LCD having an optical compensator and a multi-domain LCD have been proposed to cope with this problem. Nevertheless, such LCDs are not capable of solving the problem in a variation of the contrast ratio and color shifting.
An in-plane switching mode LCD to realize a wide viewing angle has also been proposed in the JAPAN DISPLAY 92 Page 457, Japanese Patent Unexamined Publication No. 7-36058, Japanese Patent Unexamined Publication No. 7-225538, and ASIA DISPLAY 95 Page 707.
A conventional in-plane switching mode LCD will now be explained with reference to FIGS. 1 to 3.
Referring first to FIGS. 1 and 2, operation of the conventional LCD will be described as follows. Liquid crystal molecules 8 in a liquid crystal layer 12 are aligned to have a rubbing direction(xcex8R) of 90xc2x0 less than xcex8R less than 180xc2x0 with respect to a longitudinal elongation direction (0xc2x0) of a gate bus line on a substrate as shown in FIG. 2. A polarization axis direction (xcex8PL2) of a analyzer 10 attached on a second substrate 5 is parallel to the rubbing direction (xcex8R). A polarization axis direction (xcex8PL1) of a polarizer 9 attached on the first substrate 1 is perpendicular to a polarization axis direction (xcex8PL2) and electrode elongation directions (xcex8EL) of a data electrode 2 and a common electrode 1 are xcex8EL=90xc2x0 with respect to the longitudinal elongation direction of the gate bus line. Thus, when a voltage is not applied to a data electrode 2 and a common electrode 3 as shown in FIG. 1A, the liquid crystal molecules 8 are aligned with a slightly tilted direction relative to the elongation direction (xcex8EL) of the data and common electrodes along with the rubbing direction (xcex8R) in the substrate. The elongation direction (xcex8EL) of the electrodes is perpendicular to the longitudinal direction of the gate bus line. Conversely, when a voltage having a horizontal electric field parallel to the longitudinal direction of the gate bus line is applied to the liquid crystal layer 12 as shown in FIG. 1B, the liquid crystal molecules 8 near the first substrate are rotated and a transmittance of the liquid crystal layer 12 is changed by a birefringence. A retardation value (xcex94nd) of the liquid crystal layer 12 is about xcex/2(for example, xcex94nd would be approximately 0.21-0.36 xcexcm, where xcex is a wavelength of an incident light). For example, when the liquid crystal rotation angle is about 45 degree, the transmittance is maximum so that a screen of the LCD becomes a black mode.
FIG. 3A is a plane view of the conventional in-plane switching mode liquid crystal display device and FIG. 3B is a cross-sectional view taken along the line A-Axe2x80x2 in FIG. 3A. The liquid crystal display device is protected by a metal frame 22 excluding a representing unit 21 of a liquid crystal panel 32. A gate driving circuit 23, a data driving circuit 24, and a back light housing 25 including a back light 31 are mounted on the metal frame 22. In the representing unit 21, an exposure plate 75 (shown in FIG. 3B) having a light diffusion plate, polarizer 63, first and second substrates 27 and 26 constituting the liquid crystal panel 32, and an analyzer 64 are disposed on the second substrate 26. Further, a light compensator (not shown) may be disposed between the polarizer 63 and the first substrate 27 or between the second substrate 26 and the analyzer 64 to improve the contrast ratio.
Generally, in the conventional TFT-LCD, the TFT is formed in the first substrate 27 as a switching device and the color filter is formed on the second substrate 26. However, a diode may be used as a switching device in a diode LCD and a simple matrix LCD. Alternatively, when the TFT is formed on the second substrate, the color filter is formed onto the first substrate. Further, a mono-chromiumatic LCD may also be used without the color filter.
However, the conventional in-plane switching mode liquid crystal display device has a problem of the color shifting with the change of viewing angle direction. As shown in FIGS. 1C to 1D, when a horizontal electric field is applied to the electrodes 2, 3, the liquid crystal molecules 8 nearby the first substrate 1 are aligned parallel to the longitudinal direction of the gate bus line, whereas the liquid crystal molecules 8 nearby the second substrate 5 are aligned with an angle of 90xc2x0-180xc2x0 relative to the longitudinal direction of the gate bus line. The liquid crystal molecules 8 are thus twisted. Therefore, color shifting is caused in either blue or yellow in a X or Y viewing angle direction, respectively. This color shifting mainly deteriorates the quality of the picture image.
Accordingly, the present invention is directed to a liquid crystal display device that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an in-plane switching mode liquid crystal display device having an improved picture image quality by preventing color shifting.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a liquid crystal display device includes a substrate, a gate bus line and a data bus line elongating horizontally and vertically to form a matrix figure, a pixel which is divided into several regions defined by the gate bus line and the data bus line, a data electrode and a common electrode in each region of the pixel, and alignment layer over the substrate.
In another aspect of the present invention, a liquid crystal display device includes first and second substrates, a plurality of gate bus lines and data bus lines on the first substrate, the gate bus lines being perpendicular to the data bus lines, a plurality of pixels defined by the gate bus lines and the data bus lines, the pixels having a plurality of regions, at least a pair of electrodes in each region having a common direction, and a plurality of liquid crystal molecules between the substrates.
In another aspect of the present invention, a liquid crystal display device includes first and second substrates, a plurality of gate bus lines and data bus lines on the first substrate in a matrix form, a plurality of pixels defined by the gate bus lines and the data bus lines, the pixels having first and second regions, at least one common bus line at each pixel, the common bus line being parallel to the gate bus line, at least a pair of first and second electrodes in the first and second regions, respectively, the first and second electrodes having first and second electrode elongation directions (xcex8EL1 and xcex8EL2) with respect to a longitudinal direction of the common bus line, a color filter layer over the second substrate, first and second alignment layers over the first and second substrates, the first and second alignment layers having first and second alignment directions (xcex8R1 and xcex8R2), respectively, a liquid crystal layer between the first substrate and the second substrate, a polarizer and a analyzer attached to the first substrate and the second substrate, respectively.
In another aspect of the present invention, A liquid crystal display device having a plurality of pixels each including a plurality of regions, the device includes first and second substrates, a liquid crystal molecular layer having liquid crystal molecules between the first and second substrates, a plurality of electrodes in each region of the pixels, an electric field parallel to the substrates applying to the electrodes, and first and second alignment layers over the first and second substrates, respectively, the first and second alignment layers having first and second alignment directions of xcex81 and xcex82 relative to an electrode elongating direction.
In a further aspect of the present invention, a liquid crystal display device having a plurality of pixels each including a plurality of regions, the device includes first and second substrates, a liquid crystal molecular layer having liquid crystal molecules between the first and second substrates, a plurality of electrodes on the first substrate in each region of the pixels, an electric field parallel to the substrates applying to the electrodes, a different electric field from that of a neighboring region to rotate the liquid crystal molecules in opposite directions in each neighboring region applying to the electrodes in each region, and first and second alignment layers over the first and second substrates, the first and second alignment layers providing for first and second alignment directions of xcex81 and xcex82.